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1. Introduction
A Review of Significant Advances in Areca Fiber Composites
Narayanan Gokarneshan, Venkatesan Sathya, Jayagopal Lavanya, Shaistha Shabnum, Habeebunisa and Sona M. Anton
Abstract
This chapter provides a comprehensive review of the recent developments in the design of areca fiber composites. The physical, mechanical, and thermal properties of areca fiber and its composites are explained here. The species of Areca fiber represents the Arecaceae/Palmae family (like the coconut/palm trees), with regard to its physical and mechanical properties. Researchers identified that areca fiber holds prospective applications as an alternative to reinforced polymer composites in the automotive, aerospace, and construction industries. Surveys on bio-softening, adhesion, the effects of fiber length, chemical treatments of long areca fibers, the influence of mercerization on the tensile strength of long and short areca fibers, and areca husk have been done.
Several researchers have utilized various natural fibers in developing bio-composites.
Furthermore, the reinforced composite of natural fiber is a prospective research area, considering its mechanical properties, tensile strength, lightweight, nominal pricing, biodegradable/eco-friendly nature, and ease of procuring raw materials compared to synthetic fiber-reinforced composites. However, little research has been done on areca leaf fibers as a feasible fiber. This chapter provides information on the development and investigation of the mechanical behaviour of a natural fiber-reinforced epoxy composite of areca fiber with various configurations of areca fiber orientation.
Keywords: areca fibers, natural fibers, mechanical properties, hybrid composites, chemical treatment, thermal properties
methods to eliminate or utilize solid wastes, particularly with polymers that are non- reversible in nature. The methods adopted in splitting up the wastes do not seem eco- nomical and tend to generate chemicals that prove harmful. Taking into account these factors, reinforcing polymers using natural fibers seems the only option that could result in solving the issue. Regular strands are easily available and reusable, have less thickness, and are ecofriendly. They possess high tensile properties and can be used to substitute the customary strands. The strong demerit of using characteristic strands for strengthening plastics is the contrariness, causing weak bondage between normal filaments and lattice gums and thus leading to low pliable characteristics. A number of theories and surface modification methods have been evolved to improve fiber- network interfacial holding and enhance malleable characteristics of the composites.
Further, it is proved that the strength and stiffness of the natural fiber polymer composites are mainly influenced by the loading of fiber. Up to a particular extent, there is a rise in mechanical properties with increasing fiber weight ratio. In order to evaluate the tensile properties of natural fiber reinforced composites, mathematical models/finite element models are being adopted as a necessity.
Natural fiber comprises cellulose, lignin, pectin, and so on. Owing to the presence of such constituents, natural fiber possesses unique features and special properties and gives high moisture percentage, which would in turn influence the fiber–matrix bonding. In order to find a solution for this problem, certain techniques of chemical treatment have been evolved and investigated so as to satisfy the properties of other man-made fibers [2–6]. When considering end uses like electrical insulation, the areca/betel nut fiber reinforced composites exhibit higher merits with regard to the latest development of composite materials [7].
The requirements of high strength to weight ratio in components prompted the development of composites, which necessitated high performance and efficiency, and in turn led to advances in different polymer matrix composites having different fiber reinforcements like carbon fiber, glass fibers, aramid, natural fibers, hybrid, and so on. Natural fiber composites assume a crucial role taking into account the factor of environment-friendly materials and the necessity to manufacture different sustain- able engineering and industry-oriented components.
Owing to their good mechanical properties and biodegradability, natural fibers have a crucial function as a reinforcement agent and are readily available in many parts of the world. A number of natural fibers such as jute, kenaf, sisal, hemp, bamboo, areca, pineapple, banana, and coir are being considered important for several research studies due to their availability and cost effectiveness for the design of a cost-effective reinforcing material [8–11]. A number of properties arise from the use of various natural fibers as a reinforcement agent in composite materials and can effectively be utilized for different end uses.
2. Evaluation of the physical, thermal, and mechanical properties The different parts of plants like bast, leaf, seed, stalk, fruit, grass, and wood yield cellulosic or lignocellulosic fibers. Fruits of plants yield fibers that are normally short, light, and hairy; bast (found in the stem or trunk) yields long fibers that offer strength to the plant or tree. Sturdy and rough fibers are obtained from leaves and are normally utilized in the transportation and automotive sectors. Fiber length is consid- ered important for use of the fiber, particularly in the traditional fiber industries [12].
High-quality fabrics can be designed from yarns spun by long fibers (clothing, laces,
domestic textiles, tents, sailcloth), whereas fibers like cotton, flax, hemp, ramie, and sisal can be used for production of coarser fabrics such as bagging, floor coverings, and carpets. Fibers such as jute, sisal, cotton, and hemp can be considered for cord- age fiber, tying twine, rope, and binder twine [13, 14]. Also, sisal and coir fibers can be utilized in brushes and for weaving to produce hats, mats, baskets, and rugs [15].
Such fibers have also been utilized as fillers in upholstery, for seams in vessels, barrels, and piping and as reinforcement for plastic and wallboard.
Moreover, natural fibers can be used with wood pulp in manufacturing paper [16]. Investigations on natural fibers, particularly kenaf, jute, and bamboo, have increased over the past few years [17–23]. For instance, an investigation relating to the ballistic impact resistance of kenaf reinforced polyvinyl butyral composites; a study of flexural strength and ductility of kenaf reinforced concrete composites; work relat- ing to the influence of kenaf hybridization with oil palm fiber reinforced an epoxy matrix on the tensile, flexural, and impact properties of the obtained composites; and research with regard to processing and manufacturing of kenaf reinforced that epoxy composites are worthy of consideration [24–26].
Studies have been carried out on fiber hybridization relating to kenaf and fiber- glass to find out its influence on the tensile and impact properties of the materials so produced [27]. Besides, a number of workers also reported on the use of natural fibers in the design of industrial safety helmets [28].
Previous investigations on natural fibers have shown scanty research carried out on areca and other species from the Palmae family having identical properties.
Despite the abundance of areca palm in South East Asia and the Pacific region, its fiber has not still attracted much attention and is presently being less used than other palm tree fibers [19].
It has been found that less substantial research has been conducted with regard to the optimization of surface treatment, production technique, and application of areca fiber as a reinforcing material in composites. At present, very little literature is avail- able on areca fiber used as reinforcement in composites, which implies that in spite of its innumerable merits, the fiber is at present used less. The fiber enjoys merits like recyclability; renewability; sustainability; economy; wide availability; high-potential perennial crop; inherited qualities; superior properties; mechanical properties that compare well with those of other fibers like kenaf, jute, and coir; and also complete biodegradability [29]. Statistics shows that the annual world production of areca nuts is 1,073,000, and approximately 2.5 g of areca husk could be extracted from every areca betel nut [9]. The annual statistics on world natural fiber production shows the least production of areca husk fibers in comparison with other natural fibers, like jute, coir, and kenaf, which could be ascribed to the consumption of betel nuts in the tropical Pacific and Eastern Africa and Asia.
Areca catechu is known by various names like areca palm, areca nut palm, and betel palm. It is also called Pinang in Malaysia. A. catechu is found largely in the tropical Pacific, Eastern Africa, and Asia, particularly in Malaysia, Philippines, India, and Sri Lanka. As per the statistical data provided by the Food and Agriculture Organization of the United Nations, India, Myanmar, Bangladesh, China, and Indonesia are
considered the major producers of betel nut [30]. Sri Lanka and India are the two countries where A. catechu trees are well grown, and the people of these countries use betel nut as a complement to betel leaves smeared with limestone paste [31]. But betel nut fibers are used as housing insulation material in a traditional way in certain countries [32]. Areca fruit finds a number of medical applications that include dental implants, drugs for wounds, healing of sores, diphtheria, heavy menstrual blood
flow, diarrhea, and ulcers [33]. On the other hand, biodegradable disposable plates are made from areca leaf sheaths, which fall naturally from the trees, or green waste. As the use of plastic is banned in India, areca plates are widely used. Besides India, other countries including China, Vietnam, Ukraine, Sri Lanka, Malaysia, and the United Arab Emirates manufacture these plates.
The areca tree can reach a height of 10 to 20 m, with an erect stem that is single and thin, having a diameter ranging between 10 to 15 cm with impressions of annu- lated scars of fallen leaf sheaths or fronds.
The leaves span a length between 150 and 200 cm; having many pinnate-shaped leaves, the upper part normally shows 8 to 12 fronds. Fully grown areca trees measure up to 15 m. But the conditions of soil mainly influence the growth of such trees [34, 35].
A. catechu is a monocotyledonous plant that belongs to the species of the Areca and plant family of Arecaceae or Palmae [36]. It relates to the species of oil palm, date palm, coconut palm, and others. On the whole, the plants from the Palmae family can be con- sidered tropical trees, shrubs, and vines, normally with a tall columnar trunk, bearing a crown of huge leaves. Many investigations have been carried out on the use of plant fibers extracted from the plant family. They point to the prospect of A. catechu fibers to be used as an option as reinforcement in natural fiber-based composites [37–40].
2.1 Thermal properties of areca fibers
In the design of natural fiber composites, thermal stability is considered crucial. It can decide the selection of compatible processing techniques for fibers and compos- ites. Hence, thermal properties act as a guideline during the entire design process and prevent the temperature from rising above the degradation temperature of the fiber, since it could decrease the performance of the fibers and the composites.
The fiber is found to be thermally stable up to 230°C, as evinced by lack of weight loss after the minor loss caused by moisture evaporation. Beyond this point, there is occurrence of polymerization and degradation processes of hemicelluloses and cellulose up to 330°C. Analysis of the DTG curve shows small peaks at 273.4 and 325.8°C and reveals the pyrolysis, decomposition, and degradation of hemicelluloses and cellulose. It is found that the kinetic activation energy for areca fibers falls in the range set for natural materials.
The value is indicative of areca fibers possessing excellent thermal stability, which permits it to undergo the polymerization process in the production of composites.
At a temperature of about 325°C, the burning of fiber has been evinced, which is a reasonably high temperature for polymer processing to manufacture composites.
2.2 Mechanical properties of areca fiber
Single fiber tensile testing has been used to evaluate the mechanical properties and provide some basic information necessary for the design of the potential use of plant fibers. Areca fibers have been compared with coir and palm leaf fibers with regard to the mechanical properties, particularly tensile strength. This could be attributed to its high crystallinity index and spiral angle. Considering application in reinforcement, the greater strain and low modulus of areca husk fiber offer superior toughness. The results indicate that areca fiber can substitute reinforced polymer composites, similar to other representatives from the family of Palmae/Arecaceae.
On the other hand, chemical modification also determines the mechanical proper- ties of the fiber. The untreated and alkali-treated fibers in selected concentration and
weight have been characterized, and the changes undergone by the removal or mini- mization of non-cellulose components, like hemicellulose, lignin, and wax pectin, and other impurities from the fiber surface have been described [41–43]. The modi- fication results in surface roughness and fibrillation due to the exclusion of cement- ing materials that lead to improved mechanical properties of the fiber reinforced composite [42]. 5% alkali-treated fiber has been found to exhibit the greatest tensile strength and modulus based on tensile characterization of untreated and treated areca leaf stalk fibers. This could be attributed to the disruption of hydrogen bonds in the fiber network. But a reduction in tensile strength has been observed with a rise in alkali concentration above the optimum. The tensile strength of individual fibers has been enabled by the increase in the pores and pits on the surface of fibers. Also, benzoylation treatment is found to yield better tensile properties in comparison with the alkali-treated and untreated short areca sheath fibers. The FTIR studies reveal that the absorption of alkali and benzyolation treatments have decreased the (−OH) groups compared to in the case of the untreated fiber, due to the removal of hemicel- luloses. Further, the presence of phenyl nucleus has been noticed, while the C − H deformation from lignin confirmed its removal, and the aromatic ring associated with the C − O bond demonstrated the removal of hemicellulose and pectin.